I'm not sure your intent and use until replacing pans (if ever), but I used EvapoRust purchased from Summit Racing and was very pleased with the final outcome. It was very easy to use and a quick, easy, eco-friendly cleanup. It revealed more rust than I though I had in the pans...no holes at the start to small pin holes after application. I live in the NV desert and don't plan on using it in the winter snow so I never covered up the ugly rust marks with fresh paint (didn't want to hide anything).
Here's the start/finish pics but by what I can tell, stopped the progression of it and in some spots completely took it dow to bare metal.